[Xen-devel] [PATCH v5 12/14] xen/arm: p2m: Clean cache PT when the IOMMU doesn't support coherent walk

[Julien Grall <julien.grall@xxxxxxxxxx>]

Some IOMMU don't suppport coherent PT walk. When the p2m is shared with
the CPU, Xen has to make sure the PT changes have reached the memory.

Introduce new IOMMU callback that will retrieve the IOMMU feature for a
specified domain.

On ARM, the platform can contain multiple IOMMUs. Each of them may not
have the same set of feature. The domain parameter will be used to get the
set of features for IOMMUs used by this domain.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Xiantao Zhang <xiantao.zhang@xxxxxxxxx>

---
    Changes in v5:
        - Flush on every write_pte instead of unmap page. This will
        avoid to flush a whole page when only few bytes are modified
        - Only get iommu feature once.
        - Add bits to flush cache when a new table is created
        - Fix typoes in commit message and comment
        - Use an enum to describe the feature. Each items are a bit
        position

    Changes in v4:
        - Patch added
---
 xen/arch/arm/p2m.c              |   36 ++++++++++++++++++++++++++++--------
 xen/drivers/passthrough/iommu.c |   11 +++++++++++
 xen/include/xen/iommu.h         |    9 +++++++++
 3 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 816da21..4331866 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -253,9 +253,15 @@ static lpae_t mfn_to_p2m_entry(unsigned long mfn, unsigned 
int mattr,
     return e;
 }
 
+static inline void p2m_write_pte(lpae_t *p, lpae_t pte, bool_t flush_cache)
+{
+    write_pte(p, pte);
+    if ( flush_cache )
+        clean_xen_dcache(*p);
+}
+
 /* Allocate a new page table page and hook it in via the given entry */
-static int p2m_create_table(struct domain *d,
-                            lpae_t *entry)
+static int p2m_create_table(struct domain *d, lpae_t *entry, bool_t 
flush_cache)
 {
     struct p2m_domain *p2m = &d->arch.p2m;
     struct page_info *page;
@@ -272,11 +278,13 @@ static int p2m_create_table(struct domain *d,
 
     p = __map_domain_page(page);
     clear_page(p);
+    if ( flush_cache )
+        clean_xen_dcache_va_range(p, PAGE_SIZE);
     unmap_domain_page(p);
 
     pte = mfn_to_p2m_entry(page_to_mfn(page), MATTR_MEM, p2m_invalid);
 
-    write_pte(entry, pte);
+    p2m_write_pte(entry, pte, flush_cache);
 
     return 0;
 }
@@ -308,6 +316,13 @@ static int apply_p2m_changes(struct domain *d,
     unsigned int flush = 0;
     bool_t populate = (op == INSERT || op == ALLOCATE);
     lpae_t pte;
+    bool_t flush_pt;
+
+    /* Some IOMMU don't support coherent PT walk. When the p2m is
+     * shared with the CPU, Xen has to make sure that the PT changes have
+     * reached the memory
+     */
+    flush_pt = need_iommu(d) && !iommu_has_feature(d, 
IOMMU_FEAT_COHERENT_WALK);
 
     spin_lock(&p2m->lock);
 
@@ -334,7 +349,8 @@ static int apply_p2m_changes(struct domain *d,
                 continue;
             }
 
-            rc = p2m_create_table(d, &first[first_table_offset(addr)]);
+            rc = p2m_create_table(d, &first[first_table_offset(addr)],
+                                  flush_pt);
             if ( rc < 0 )
             {
                 printk("p2m_populate_ram: L1 failed\n");
@@ -360,7 +376,8 @@ static int apply_p2m_changes(struct domain *d,
                 continue;
             }
 
-            rc = p2m_create_table(d, &second[second_table_offset(addr)]);
+            rc = p2m_create_table(d, &second[second_table_offset(addr)],
+                                  flush_pt);
             if ( rc < 0 ) {
                 printk("p2m_populate_ram: L2 failed\n");
                 goto out;
@@ -411,13 +428,15 @@ static int apply_p2m_changes(struct domain *d,
 
                     pte = mfn_to_p2m_entry(page_to_mfn(page), mattr, t);
 
-                    write_pte(&third[third_table_offset(addr)], pte);
+                    p2m_write_pte(&third[third_table_offset(addr)],
+                                  pte, flush_pt);
                 }
                 break;
             case INSERT:
                 {
                     pte = mfn_to_p2m_entry(maddr >> PAGE_SHIFT, mattr, t);
-                    write_pte(&third[third_table_offset(addr)], pte);
+                    p2m_write_pte(&third[third_table_offset(addr)],
+                                  pte, flush_pt);
                     maddr += PAGE_SIZE;
                 }
                 break;
@@ -433,7 +452,8 @@ static int apply_p2m_changes(struct domain *d,
                     count += 0x10;
 
                     memset(&pte, 0x00, sizeof(pte));
-                    write_pte(&third[third_table_offset(addr)], pte);
+                    p2m_write_pte(&third[third_table_offset(addr)],
+                                  pte, flush_pt);
                     count++;
                 }
                 break;
diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c
index 59f1c3e..2faab48 100644
--- a/xen/drivers/passthrough/iommu.c
+++ b/xen/drivers/passthrough/iommu.c
@@ -344,6 +344,17 @@ void iommu_crash_shutdown(void)
     iommu_enabled = iommu_intremap = 0;
 }
 
+bool_t iommu_has_feature(struct domain *d, enum iommu_feature feature)
+{
+    const struct iommu_ops *ops = domain_hvm_iommu(d)->platform_ops;
+    uint32_t features = 0;
+
+    if ( iommu_enabled && ops && ops->features )
+        features = ops->features(d);
+
+    return !!(features & (1 << feature));
+}
+
 static void iommu_dump_p2m_table(unsigned char key)
 {
     struct domain *d;
diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
index b7481dac..2a763ae 100644
--- a/xen/include/xen/iommu.h
+++ b/xen/include/xen/iommu.h
@@ -67,6 +67,14 @@ int iommu_map_page(struct domain *d, unsigned long gfn, 
unsigned long mfn,
                    unsigned int flags);
 int iommu_unmap_page(struct domain *d, unsigned long gfn);
 
+enum iommu_feature
+{
+    IOMMU_FEAT_COHERENT_WALK = 1,
+};
+
+bool_t iommu_has_feature(struct domain *d, enum iommu_feature feature);
+
+
 #ifdef HAS_PCI
 void pt_pci_init(void);
 
@@ -139,6 +147,7 @@ struct iommu_ops {
     void (*iotlb_flush)(struct domain *d, unsigned long gfn, unsigned int 
page_count);
     void (*iotlb_flush_all)(struct domain *d);
     void (*dump_p2m_table)(struct domain *d);
+    uint32_t (*features)(struct domain *d);
 };
 
 void iommu_suspend(void);
-- 
1.7.10.4


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